$$3(y-5)^{2}+5y=(2y-3)^{2}-(y+1)^{2}+1$$
$y=6$
$$3\left(y^{2}-10y+25\right)+5y=\left(2y-3\right)^{2}-\left(y+1\right)^{2}+1$$
$$3y^{2}-30y+75+5y=\left(2y-3\right)^{2}-\left(y+1\right)^{2}+1$$
$$3y^{2}-25y+75=\left(2y-3\right)^{2}-\left(y+1\right)^{2}+1$$
$$3y^{2}-25y+75=4y^{2}-12y+9-\left(y+1\right)^{2}+1$$
$$3y^{2}-25y+75=4y^{2}-12y+9-\left(y^{2}+2y+1\right)+1$$
$$3y^{2}-25y+75=4y^{2}-12y+9-y^{2}-2y-1+1$$
$$3y^{2}-25y+75=3y^{2}-12y+9-2y-1+1$$
$$3y^{2}-25y+75=3y^{2}-14y+9-1+1$$
$$3y^{2}-25y+75=3y^{2}-14y+8+1$$
$$3y^{2}-25y+75=3y^{2}-14y+9$$
$$3y^{2}-25y+75-3y^{2}=-14y+9$$
$$-25y+75=-14y+9$$
$$-25y+75+14y=9$$
$$-11y+75=9$$
$$-11y=9-75$$
$$-11y=-66$$
$$y=\frac{-66}{-11}$$
$$y=6$$
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